The instant invention relates to elevator installation and more specifically to an apparatus and method for accurately positioning elevator guide rails in linear and parallel orientation.
Increasingly sophisticated control systems, improved drive and braking components and constantly rising performance requirements have all combined to steadily increase the operating speed of electric, cable suspended elevators. Such increased operating speeds are not without attendant difficulties. Perhaps the most significant difficulty, certainly from a passenger comfort standpoint, is rapid, random lateral motion of the car during its vertical traverse due to irregularities in the placement of the guide rails upon which the car moves. A pair of opposed rails are disposed on the sidewalls of the elevator shaft and rollers or similar structures engage parallel faces of the rail to maintain appropriate car position. Variations in rail linearity substantially less than one-half inch due to variations in the sidewalls to which they are received, for example, can cause discomfort to passengers, particularly at higher elevator car speeds.
Significant time and effort has therefore been devoted to schemes for positioning the rails in a linear, parallel disposition on the walls of the elevator shaft. For example, a plumb line may be hung generally adjacent brackets to which the guide rails will be secured and the rails trued to the plumb line. While it is apparent that this scheme provides reasonably accurately positioned rails, it cannot ensure mounting of the rails within the narrow tolerances which are presently viewed as desirable. Furthermore, and less apparent, is the failure of such a system to accurately and commonly position the planes of opposed rails i.e., ensure that each rail is true and parallel to the other rail of a pair in addition to being linearly oriented.
U.S. Pat. No. 3,851,736 teaches an apparatus and method wherein a rig is lowered into the hoistway by a hoist and the rail sections are assembled by raising a rail approximately its own length, securing the next lower rail to the bottom of the raised rail and repeating the operation until complete car and counterweight guide rail assemblies extend from the lowermost to the uppermost portion of the hoistway. U.S. Pat. No. 4,345,671 discloses another apparatus and method for installing elevator guide rails. Here, a cone or cap is placed upon the upper end of each of the guide rails and they are raised by pushing them up approximately their own length from their lower terminus, securing an additional rail section to the lower terminus and repeating the procedure until the top of the rail is at the top of the hoistway. Here, too, the support unit or platform is utilized to position the guide rails prior to their securement to the hoistway walls.
A review of these patents as well as other prior art activity relating to uniform linear and parallel guide rail placement in a hoistway reveals certain shortcomings and the desirability of new apparatus and methods.